There must have been some pretty good reasons to reverse such a staunch view on OFs and Mark was kind enough to elaborate in an open letter to the community. It simply comes down to being able to better support the players of WAR. Apparently, Mythic is also willing to invest in paid full and part-time moderators and a powerful forum platform to ensure these internal support boards don't become a cesspool of hate and discrimination.
Here's Mythic's official twist. The forums will be very light-weight graphically. They will not run ads of any sort. There will be a strict code of conduct, but it won't hamper constructive negative feedback. Anyone familiar with the Warhammer Online beta boards should feel quite at home. Only active subscribers will be able to post. You can "level up" on these forums by contributing to intelligent discussion. This will give you access to special boards where Mark and the other devs will post frequently. More details on Mythic's official forums will be coming shortly, but you can expect to see them in action during February's public test of the 1.2 patch. I wonder what this will mean for the unofficial forums.